Liquid density measuring system

TRE Measurements has announced a liquid density measurement system for applications requiring accurate measurement of the specific gravity of mixtures of water and alcohol.

Online measurement of specific gravity is generally considered quite difficult. Techniques based on vibrating rods and similar methods are strongly affected by liquid viscosity as well as density.

The solution lies in the float that sits at a depth in the solution that is dictated by the specific gravity of the liquid. Its exact position is measured by using an ultrasonic displacement transducer. The ultrasonic transducer is placed 140 mm above and bounces its sound waves off the disc. The arrangement determines the float position to an accuracy of 0.5 mm.

In printing machine applications, composition of water and alcohol mixture is controlled by opening a solenoid valve to admit more alcohol if there is too little, or by allowing alcohol to evaporate if there is too much. The same approach is equally available to the brewing and other chemical and process industries.